Roedy Green has a funny (and very long) guide called How To Write Unmaintainable Code [Ensure a job for life ;-)]
Make sure that every method does a little bit more (or less) than its name suggests. As a simple example, a method named isValid(x) should as a side effect convert x to binary and store the result in a database.
a naming convention from the world of C++ is the use of "m_" in front of members. This is supposed to help you tell them apart from methods, so long as you forget that "method" also starts with the letter "m".
Use an "o" or "obj" prefix for each instance of the class to show that you're thinking of the big, polymorphic picture.
"Much of the skill in writing unmaintainable code is the art of camouflage, hiding things, or making things appear to be what they are not. Many depend on the fact the compiler is more capable at making fine distinctions than either the human eye or the text editor. Here are some of the best camouflaging techniques."